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Table 2 Overview of electron donor specificity of MtLPMO9A, MtLPMO9B or MtLPMO9C

From: Lytic polysaccharide monooxygenases from Myceliophthora thermophila C1 differ in substrate preference and reducing agent specificity

Group No. Reducing agent MtLPMO9A MtLPMO9B MtLPMO9C
Activity compared to ascorbic acid %
C1-/C4-ox and non-ox C1-ox C4-ox Non-ox C1-/C4-ox and non-ox C1-ox Non-ox C1-/C4-ox and non-ox C4-ox Non-ox
I 1 3-Hydroxy-4-methoxycinnamic acid 0 0 0 0 0 0 0 0 0 0
2 Homovanillic acid 0 0 0 0 0 0 0 0 0 0
3 Naringin 0 0 0 0 0 0 0 0 0 0
4 p-coumaric acid 0 0 0 0 0 0 0 0 0 0
5 Sinapic acid 23 23 31 24 4 3 14 15 12 18
6 Syringic acid 0 0 0 0 0 0 0 0 0 0
7 Vanillic acid 0 0 0 0 0 0 0 0 0 0
II 8 (−)-Epicatechin 77 68 90 27 21 19 34 21 15 26
9 (+)-Catechin 43 47 41 24 7 6 17 6 5 7
10 3,4-Dihydroxybenzaldehyde 9 13 7 0 0 0 0 0 0 0
11 3,4-Dihydroxybenzoic acid 13 15 13 0 1 1 2 4 5 3
12 3,4-Dihydroxycinnamic acid 0 0 0 0 49 48 63 0 0 0
13 3,4-Dihydroxyphenylacetic acid 92 79 105 68 18 17 31 12 9 14
14 3-Methylcatechol 102 87 121 49 22 20 38 14 15 12
15 4-Chlorocatechol 72 68 75 74 8 7 24 24 21 26
16 Caffeic acid 49 49 52 20 8 7 26 0 0 0
17 Carminic acid 8 7 8 21 0 0 0 3 2 4
18 Catechol 65 57 75 26 8 7 18 11 12 10
19 Chlorogenic acid 36 38 36 25 4 3 18 0 0 0
20 Dopamine hydrochloride 93 71 105 132 46 45 57 6 2 10
21 l -3,4-Dihydroxyphenylalanine 101 75 123 86 79 78 84 33 26 41
22 Quercetin 0 0 0 0 0 0 0 0 0 0
23 Taxifolin 0 0 0 0 15 15 20 4 3 4
24 Resorcinol 0 0 0 0 0 0 0 0 0 0
25 Hydroquinone 51 55 51 25 2 1 10 5 4 7
III 26 Gallic acid 81 72 94 38 46 45 54 22 18 26
27 (−)-Epigallocatechin-gallate 76 56 97 30 79 79 83 11 9 12
28 Tannic acid 0 0 0 0 18 13 66 0 0 0
IV 29 Reduced glutathione 0 0 0 0 16 15 30 8 7 8
30 l -cysteine 16 23 13 0 22 20 40 6 7 4
31 Allyl iso-thiocyanate 0 0 0 0 0 0 0 0 0 0
32 d-methionine 0 0 0 0 0 0 0 0 0 0
V 33 Ascorbic acid 100 100 100 100 100 100 100 100 100 100
  Peak area (nC x min)a (0.897) (0.460) (0.058) (0.360) (3.273) (2.962) (0.311) (1.542) (0.760) (0.781)
34 d-quinic acid 0 0 0 0 0 0 0 0 0 0
  1. The total sum of integrated peak areas of released oxidized (C1-ox, C4-ox) and non-oxidized (non-ox) and both (ox and non-ox) gluco-oligosaccharides from RAC, incubated with either MtLPMO9A, MtLPMO9B or MtLPMO9C in the presence of ascorbic acid, was taken as a reference and equals to 100 % of the LPMO activity. The numbers correspond to the relative activity of MtLPMO9A, MtLPMO9B or MtLPMO9C compared to ascorbic acid (total sum integrated peak areas of released oxidized and non-oxidized gluco-oligosaccharides of a reducing agent compared to ascorbic acid (areas from Fig. 5). Auto-oxidation of RAC was absent for all reducing agents tested based on the absence of oxidized or non-oxidized gluco-oligosaccharides. Reducing agents that can donate electrons to all three LPMOs are highlighted in italics. See “Methods” for details about the activity assays
  2. aIntegrated peak areas of released C1-, C4-oxidized and non-oxidized gluco-oligosaccharides after incubation of MtLPMO9A, MtLPMO9B and MtLPMO9C with RAC in the presence of 1 mM ascorbic acid based on HPAEC (Fig. 5)